This undated U.S. Air Force illustration shows the X-51A Waverider. The hypersonic plane's flight was a failure, according to the U.S. Air Force. (AFP)

The U.S. Air Force’s X-51 hypersonic test aircraft failed during its latest launch over the Pacific Ocean.

A B-52 bomber flying over the Point Mugu Naval Air Warfare Center Sea successfully launched the X-51 — called the Waverider — in the late morning on Aug. 14, the Air Force said in an Aug. 15 statement. But 16 seconds later, “a fault was identified with one of the cruiser control fins.”

After being released by the B-52, a rocket boosts the X-51 before its scramjet, hypersonic engine kicks in. But once the rocket separated from the X-51 this week, testers were unable to control the Waverider due to the broken fin and the aircraft was lost.

“It is unfortunate that a problem with this subsystem caused a termination before we could light the Scramjet engine,” Charlie Brink, X-51A program manager for Air Force Research Laboratory, said in the statement. “All our data showed we had created the right conditions for engine ignition and we were very hopeful to meet our test objectives.”

Program officials are working to determine the cause of the failure.

The Air Force has not had problems with X-51 fins during the prior two test flights of the X-51. In May 2010, an X-51 flew for more than three minutes at Mach 4.88.

The X-51 is built by Boeing. Pratt & Whitney Rocketdyne makes the hypersonic engine.